A steadily increasing volume of cargo is transported by truck trailer and must be loaded into the trailer at its origin, unloaded from the trailer at freight terminals, and then sometimes reloaded on a local delivery truck and subsequently unloaded at its final destination. Where possible, cargo is placed on pallets which are carried by front-end loaders into and out of the truck trailers. While such loading is relatively fast, it possesses a notable risk factor for the operator and others who must operate the loader in narrow, often poorly lighted trailers in close proximity to heavy objects which can easily fall or tip within the trailer. When the cargo is of a type impossible to handle with a front-end loader or one which is not easily shipped on pallets, the cargo must be loaded on the trailer by hand labor. In any event, the cargo is always transferred from the loading dock to the trailer starting with the loading of the front end of the trailer and progressing rearwardly until the trailer has been filled to the doors at the rear cargo entrance, a distance of up to 50 feet. If loading by hand, a laborer must make many trips back and forth along the 50-foot trailer before it is filled to capacity. It has been estimated that six men can work for approximately six hours to completely load a 50-foot, over-the-road truck trailer, and such loading is very tedious for the cargo handlers and understandably expensive for the trucking companies.
Even if hand loading and unloading can be avoided and front-end loaders carry the cargo into and out of the trailers, a high element of risk is present when a 5,000 pound front-end loader enters the truck van carrying an additional load of several thousand pounds. An operator may not know until it is too late whether the truck flooring will hold the combined weight of the front-end loader and cargo, and any tipping or overturning of the heavily loaded loader in the narrow confines of the often darkened and crowded van interior can be extremely perilous. Often the driver of the front-end loader is assisted by a second worker who leads the front-end loader to inspect the necessary clearances and light the way while directing the driver of the loader. Accidents in which the lead workman is pinned against cargo or sidewalls or where cargo falls on him are not unusual, and accordingly, it is desirable to be able to load such trailers without driving the front-end loaders into the trailer.
When cargo is unloaded from the truck trailer at freight terminals or at the final destination, the unloading of the trailer presents the same dangers and difficulties as those described for loading. With large and heavy loads, many men or heavy equipment may be required to unload the trailer and many man-hours consumed while the expensive truck trailer remains idle and unable to continue its delivery missions until a substantial part of the load has been removed.
It is, therefore, highly desirable to be able to provide a truck trailer or other storage facility in which it is unnecessary to move cargo to the far end of the cargo space either by hand or by means of a front-end loader. It is also desirable to reduce the total number of man-hours required for loading or unloading various types of conveyors as have been proposed in the prior art, as solutions to these problems; the present invention offers improvements over such prior art devices.